1. Field of the Invention
The invention generally relates to a semiconductor device, and more particularly, to a semiconductor device capable of being operated at a high voltage without a large substrate current.
2. Description of Related Art
Semiconductor design has to be improved along with increasing integration and increasing complicated requirements thereof. For example, the design of high voltage devices must enable the high voltage devices to operate at a high voltage without effecting operation of other devices as well as large substrate currents.
FIG. 1 is a schematic view of a switch device formed by two high voltage n-type metal-oxide-semiconductors (HV-NMOS). Referring to FIG. 1A, the switch device 10 includes a high-side HV-NMOS 12 and a low-side HVNMOS 14, wherein a drain of the high-side HV-NMOS 12 is electrically connected to a system power Vcc, and a source of the high-side HV-NMOS 12 is electrically connected to an output pad Vo and a drain of the low-side HV-NMOS 14. However, when the switch device 10 is switched, the high-side HV-NMOS 12 is turned on. Meanwhile, a voltage level of the output pad Vo is affected by an external load, such as an external inductor, coupled thereto, so that overshoot occurs at the source of the high-side HV-NMOS 12. As a result, the voltage level of the source of the high-side HV-NMOS 12 is soon raised higher than the system power Vcc, so that a highly large substrate current is generated in the high-side HV-NMOS 12.
Accordingly, the high voltage device applied to the switch device may have a highly large substrate current while being operated at the high voltage. Moreover, the operation of any semiconductor device may possibly effect the operation of any others. It is thus desired to provide an improved solution addressing the above-mentioned issues.